Proteins are the principal operatives within cells, involved in carrying out essentially all biological functions. A complex network of intra- and intermolecular interactions, post-translational modifications and abundance levels is required to maintain the delicate balance of function essential for life. Subtle changes within this network can give rise to specific biological responses to environmental factors, onset of disease, normal aging, and other biological processes. Therefore, direct experimental observation of protein structures and interactions in relation to biological function is paramount to improved understanding of living systems.
The versatility of protein function has its origins in topological shapes and features that these polymeric macromolecules can adopt. Moreover, the crowded intracellular environment profoundly influences their shape such that proteins that appear unstructured in vitro can adopt a more defined conformation inside cells. These induced topological features occur as a consequence of interaction within cellular compartments that may not be replicated in cell lysates or purified components.
Thus, there is a need in the art for methods that can reveal information about global protein topology under physiologically relevant conditions within native interactions and with intended partners inside cells, and a further need for methods that can do so with high sensitivity, specificity, and efficiency on a large scale.